Apparatus, system, and method for transcutaneously transferring energy

ABSTRACT

An apparatus for transcutaneously transferring an amount of energy to an implantable orthopaedic device includes a primary coil. The primary coil has a resonant frequency matched to a resonant frequency of a secondary coil, which may form part of the implantable orthopaedic device. The primary coil may have an aperture configured to receive a portion of a patient&#39;s body or may include a substantially “C”-shaped core. A power circuit may be coupled with the primary coil to provide power to the coil. The apparatus may also include a wireless receiver, a measuring device, and/or a display.

This application is a divisional of U.S. patent application Ser. No.11/172,316, filed on Jun. 30, 2005. That application is incorporated inits entirety herein by reference.

CROSS-REFERENCE TO RELATED U.S. PATENT APPLICATION

Cross-reference is made to U.S. Utility patent application Ser. No.11/171,869 entitled “Apparatus, System, and Method for TranscutaneouslyTransferring Energy” which was filed Jun. 30, 2005 by Jason T. Sherman,the entirety of which is expressly incorporated herein by reference.Cross-reference is made to U.S. Utility patent application Ser. No.12/788,655 entitled “APPARATUS, SYSTEM, AND METHOD FOR TRANSCUTANEOUSLYTRANSFERRING ENERGY,” which was filed on May 27, 2010 by Jason T.Sherman (265280-209270), the entirety of which is expressly incorporatedherein by reference.

TECHNICAL FIELD

The present disclosure relates generally to transcutaneous energytransfer devices and methods, and more particularly to devices andmethods for transcutaneously transferring energy to an implantablemedical device.

BACKGROUND

Transcutaneous energy transfer (TET) devices are used to transfer energyacross a boundary such as skin and other tissue of a patient. Forexample, a TET device may be used to transfer energy from a sourceexternal to a patient's body to a device implanted in the patient's bodyto power and/or recharge the device. Because the implanted devicereceives power transcutaneously, the implanted device typically does notrequire an implanted power source, such as a battery, to operate. Assuch, the patient is relieved from continual surgical operations toreplace and/or recharge the implanted battery or other power sources.

SUMMARY

According to one aspect, an apparatus for transcutaneously transferringan amount of energy to an implantable orthopaedic device is disclosed.The apparatus may include a primary coil. The primary coil may have anaperture configured to receive a portion of a patient's body such as aleg, an arm, or the torso of the patient. The aperture may have, forexample, an inner diameter of six inches or greater. Alternatively, theprimary coil may be wound around a portion of a substantially “C”-shapedcore. The “C”-shaped core may be, for example, a ferrite core. The coremay include an elongated middle portion, which may be sized based on alength of the secondary coil of the implantable orthopaedic device. Thecore may also include two end portions extending substantiallyorthogonally from opposite distal ends of the elongated middle portion.In some embodiments, the primary coil may be coupled with a limb bracesuch as a leg or knee brace.

The primary coil may have a resonant frequency matched to a resonantfrequency of a secondary coil of the implantable orthopaedic device. Theresonant frequencies may be matched by use of a capacitive device suchas a capacitor. In some embodiments, the resonant frequency of theprimary coil is adjustable to match the resonant frequency of additionalsecondary coils.

The implantable orthopaedic device may include an electrical circuitconfigured to receive power from the secondary coil. For example, theelectrical circuit may include a transmitter configured to transmit datain response to a power signal received from the secondary coil.

The apparatus may further include a power circuit which may supply apower signal to the primary coil to generate an alternating magneticfield. The power circuit may include a wireless receiver configured toreceive data signals from the implantable orthopaedic device, ameasuring device configured to measure an amount of power used by theprimary coil, and/or a display configured to display the amount of powerto a caregiver or user of the apparatus. In some embodiments, the powercircuit includes a direct current power source and a converterconfigured to convert the direct current power source to an alternativecurrent power signal. In such embodiments, the primary coil and thepower circuit may be included in a portable housing.

According to another aspect, a method for determining a location of anorthopaedic device implanted in a patient's body is disclosed. Themethod may include moving or sweeping a primary coil over the patient'sbody or portion thereof. The amount of power used by the primary coilmay be measured while the primary coil is being moved. The location maythen be determined based on the amount of power used by the primarycoil. That is, the location of the implanted orthopaedic device may bedetermined based on when the amount of power used by the primary coil isat or above a predetermined threshold value (e.g., a user definedmaximum value). The method may further include tuning a resonantfrequency of the primary coil to match a resonant frequency of asecondary coil of the implanted orthopaedic device. The method may alsoinclude receiving a wireless data signal from the implanted orthopaedicdevice.

The above and other features of the present disclosure, which alone orin any combination may comprise patentable subject matter, will becomeapparent from the following description and the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description particularly refers to the following figures,in which:

FIG. 1 is a diagrammatic view of a transcutaneous energy transfersystem;

FIG. 2 is a perspective view of one embodiment of the primary coil ofthe transcutaneous energy transfer system of FIG. 1;

FIG. 3 is a cross-sectional view taken generally along section lines 3-3of FIG. 2 (note the patient's limb is not shown for clarity ofdescription);

FIG. 4 is a perspective view of a leg brace having the primary coil ofFIG. 2 coupled therewith;

FIG. 5 is a perspective view of another embodiment of the primary coilof the transcutaneous energy transfer system of FIG. 1;

FIG. 6 is a cross-sectional view taken generally along section lines 6-6of FIG. 5;

FIG. 7 is an elevational view showing the primary coil of FIG. 5 beingused to transfer energy to an implanted orthopaedic device;

FIG. 8 is an elevational view of a tibial tray;

FIG. 9 is an exploded elevational view of the secondary coil and bobbinassembly of the tibial tray of FIG. 8;

FIG. 10 is a cross-sectional view taken generally along the sectionlines 6-6 of FIG. 5;

FIG. 11 is a block diagram of one embodiment of a transcutaneous energytransfer system;

FIG. 12 is a block diagram of another embodiment of a transcutaneousenergy transfer system;

FIG. 13 is a simplified flow chart of an algorithm for transcutaneouslytransferring an amount of energy; and

FIG. 14 is a simplified flow chart of an algorithm for determining alocation of an implanted orthopaedic device in the body of a patient.

DETAILED DESCRIPTION OF THE DRAWINGS

While the concepts of the present disclosure are susceptible to variousmodifications and alternative forms, specific exemplary embodimentsthereof have been shown by way of example in the drawings and willherein be described in detail. It should be understood, however, thatthere is no intent to limit the concepts of the present disclosure tothe particular forms disclosed, but on the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the appended claims.

Referring to FIG. 1, a system 10 for transcutaneously transferring anamount of energy includes a primary coil 12 and an implantableorthopaedic device 14. The implantable orthopaedic device 14 includes asecondary coil 16. Illustratively, the orthopaedic device 14 isimplanted in a leg 18 of a patient 20. However, in other embodiments,the device 14 may be implanted in any location of the patient 20. Assuch, the device 14 may be any type of implantable orthopaedic devicesuch as, for example, a tibial tray implant, a bone distractor, or thelike. Based on the particular application, the device 14 may includeother electronic circuitry and/or devices such as sensors, processors,transmitters, electrical motors, actuators, or the like.

The primary coil 12 is coupled with a power circuit 22 via a number ofinterconnects 24. The power circuit 22 provides an alternating currentpower signal to the primary coil 12 to energize the primary coil 12. Inresponse to the power signal, the primary coil 12 generates analternating magnetic field. While the primary coil 12 is positioned nearthe implanted orthopaedic device 14 such that the primary coil 12 andthe secondary coil 16 are inductively coupled, the alternating magneticfield generated by the primary coil 12 induces a current in thesecondary coil 16. In this way, energy is transferred from the primarycoil 12 to the secondary coil 16. It should be appreciated that theprimary coil 12 may be positioned such that the coil 12 inductivelycouples with the secondary coil 16 while not coming into contact withthe skin of the patient 20.

To improve the efficiency of the energy transfer between the coils 12,16, the resonant frequency of the primary coil 12 is matched to theresonant frequency of the secondary coil 16 of the orthopaedic device14. As used herein in reference to resonant frequencies, the terms“match”, “matched”, and “matches” are intended to mean that the resonantfrequencies are the same as or within a predetermined tolerance range ofeach other. For example, the resonant frequency of the primary coil 12would match the resonant frequency of the secondary coil if the currentinduced in the secondary coil 16 is sufficient to power an electricalcircuit or device coupled therewith. Conversely, the resonantfrequencies of the coils 12, 16 would not match if the current inducedin the secondary coil 16 is insufficient to power the electrical circuitor device. The resonant frequency of the primary coil 12 and thesecondary coil 16 may be configured using a capacitive device, such as acapacitor, as discussed in more detail below in regard to FIGS. 11 and12. The resonant frequency of the primary coil 12 and the secondary coil16 may be matched to any frequency. However, in some embodiments, theresonant frequency of the coils 12, 16 is configured to a frequency suchthat patient exposure to magnetic fields is reduced. For example, insome embodiments the resonant frequencies of the coils 12, 16 arematched to a resonant frequency of about 9 kilohertz or lower. In oneparticular embodiment, the resonant frequencies of the coils 12, 16 arematched to a resonant frequency of about 5 kilohertz. The frequency ofthe power signal produced by the power circuit 22 is also matched to theresonant frequency of the primary coil 12. In some embodiments, theresonant frequency of the primary coil 12 and the power circuit 22 maybe adjustable to match the resonant frequencies of other secondary coilsof other implantable orthopaedic devices. In this way, differentorthopaedic devices (i.e. the secondary coils of the orthopaedicdevices) may have different resonant frequencies to allow selectiveenergy transfer to one implanted orthopaedic device while reducing theamount of energy inadvertently transferred to other implantedorthopaedic devices (i.e., the resonant frequencies of the otherimplanted orthopaedic devices do not match the resonant frequency of theprimary coil 12). The resonant frequency of the primary coil may,however, be adjusted to match the resonant frequency of the otherimplantable devices to transfer energy to such devices.

Referring now to FIG. 2, in one embodiment, the primary coil 12 isembodied as a primary coil 26 having an aperture 28 configured toreceive a portion of the patient's 20 body. Illustratively, the aperture28 is configured to receive a leg 18 of the patient 20. However, inother embodiments, the aperture 28 may be configured to receive anyportion of the patient's 20 body including, for example, an arm, afinger, the head, or the torso of the patient 20. That is, the primarycoil 12 has an inner diameter 30, as illustrated in FIG. 3, ofsufficient length to allow the portion of the patient's 20 body to bereceived by the aperture 28 while allowing the primary coil 26 to bespaced away from the skin of the patient 20 (i.e., an air gap is presentbetween the primary coil 26 and the skin of the patient 20). In oneembodiment, the aperture 28 of the primary coil 26 may have an innerdiameter 30 greater than about six inches. In one particular embodiment,the aperture 28 has an inner diameter 30 of about 8.5 inches.

Illustratively, the primary coil 26 is toroidal in shape, but primarycoils having other shapes capable of including the aperture 28 may beused. For example, primary coils having square or rectangular shapes maybe used. The primary coil 26 is wound around a bobbin 32 as illustratedin FIG. 2. The bobbin 32 may be formed from any nonmagnetic andnonconductive material such as, for example, a plastic material. Thebobbin 32 provides a support structure for the primary coil 26 and may,similar the primary coil 26, have a toroidal shape or other shapecapable of defining an aperture configured to receive a portion of thepatient 20. The primary coil 26 is formed from individual turns. Thenumber of turns which form the primary coil 26 may vary depending uponthe particular application and required magnetic intensity. Theindividual turns are wound around the bobbin 32 and positioned in a coiltrack 34. The coil track 34 has a height 36 configured to accommodatethe number of turns. That is, the height 36 may be increased toaccommodate additional individual turns. In one particular embodiment,the height 36 of the coil track 34 has a track height 34 of about 1.5inches. To improve conductivity (i.e., reduce the effects of the “skineffect”) of the primary coil 26 at operating frequencies, the coil 26may be formed from Litz wire (i.e., wire formed from a number ofindividual strands of wire). Depending on the desired resonant frequencyof the primary coil 26, the Litz wire may have a strand count greaterthan about fifty strands. In one particular application, the primarycoil 26 is formed from Litz wire having a strand count of about 100strands. In addition, in some embodiments, the primary coil 26 may beformed from a number of individual, parallel coils to reduce the voltagerequirements of each individual coil.

In use, a portion of the patient 20, such as the leg 18, is positionedin the aperture 28 of the primary coil 26. The primary coil 26 ispositioned such that the coil 26 is substantially coplanar with theorthopaedic device 14 and circumferentially surrounds the portion of thepatient 20. For example, the primary coil 26 may be positioned such thatthe coil 26 and the secondary coil 16 of the device 14 may beinductively coupled. To do so, a caregiver (e.g., a physician, a nurse,or the like) may grasp a portion of the bobbin 32 to move the primarycoil 26 to the desired location. In some embodiments, a handle 38 may becoupled with a portion of the bobbin 32 to facilitate the positioning ofthe primary coil 26. Once the primary coil 26 is located in the desiredposition, an alternating current power signal may be applied to theprimary coil 26. In response to the power signal, the primary coil 26generates an alternating magnetic field. The power signal and primarycoil 26 are configured such that the alternating magnetic fieldgenerated by the coil 26 extends into the portion (e.g., the leg 18) ofthe patient 20. The magnetic field is received by the secondary coil 16of the orthopaedic device 14. As discussed above, the alternatingmagnetic field produces a current in the secondary coil 26 which may beused to power electrical circuitry and/or devices coupled with the coil26.

Referring now to FIG. 4, in some embodiments, the primary coil 26 may beincluded in a limb brace 40 to provide better stability for the coil 26during operation of the system 10. The limb brace 40 may be any type oflimb brace configured to couple to any limb of the patient 20.Illustratively, the limb brace 40 is a leg brace, commonly referred toas a knee brace, configured to couple to the leg 18 of the patient 20.The limb brace 40 includes a brace structure 42. The brace structure 42includes coupling means, such as straps, snaps, hook and loop fasteners,or the like, to secure the structure 42 to the leg 18 or other limb ofthe patient 20. The primary coil 26 is coupled with the bracingstructure 42 via, for example, mounting posts or the like. The primarycoil 26 may be permanently mounted to the bracing structure 42 such thatthe primary coil 26 is positioned in a similar location every time thelimb brace 40 is worn by the patient 20. Alternatively, the primary coil26 may be movable about the bracing structure 42 to allow the coil 26 totransfer energy to implantable orthopaedic devices located in regions inaddition to the knee area of the patient 20. Regardless, because theprimary coil 26 is coupled with the limb brace 40, the caregiver is notrequired to constantly hold the primary coil 26 in the desired position.Additionally, the primary coil 26 may be used to transfer energy whilethe patient 20 is performing an exercise such as walking or jogging. Inother embodiments, the primary coil 26 may be coupled with a stand orother structure to stabilize the primary coil 26 and allow the primarycoil 26 to be inserted over the portion of the patient 20 without theaid of the caregiver.

Referring now to FIGS. 5 and 6, in another embodiment, the primary coil12 may be embodied as a primary coil 46 wound around a portion of asubstantially “C”-shaped core 48. The core may be made from any ferrousmaterial such as iron, ferrite, or the like. In the illustrativeembodiment, the core 48 is formed from a unitary core having anelongated middle portion 50, a first end portion 52, and a second endportion 54. In some embodiments, the elongated middle portion 50 has alength based on the length of the secondary coil 16. The first andsecond end portions 52, 54 extend substantially orthogonally from themiddle portion 50 at opposite distal ends and are coplanar with eachother. However, in other embodiments, the substantially “C”-shaped core48 may be formed from a middle portion and two end portions coupled withthe middle portion using a suitable adhesive. Additionally, although theillustrative core 48 has a circular shaped cross-section, cores havingother geometric cross sections, such as square or rectangular, may beused in other embodiments. Regardless, the “C”-shaped core 48 isconfigured such that the magnetic field generated by the primary coil 46is increased in the direction of the end portions 52, 54. That is, themagnetic field extends further away from the primary coil 46 ins thedirection of the end portions 52, 54.

Similar to the primary coil 26, the primary coil 46 is formed fromindividual turns, which may, in some embodiments, be formed from Litzwire. The individual turns which form the primary coil 46 are woundaround the elongated middle portion 50 of the core 48. In someembodiments, an insulator film (not shown) is wrapped around the core 48prior to the primary coil 46 being wound thereon to insulate the turnsof the coil 46 from the core 48. Alternatively, in some embodiments, abobbin (not shown) having an aperture configured to receive the core 48is used. In such embodiments, the primary coil 46 is wound around thebobbin, which forms an insulative barrier between the coil 46 and thecore 48. Additionally, in some embodiments, a sleeve 56 may bepositioned around the outside of the primary coil 46 to protect the coil46. The sleeve 56 may be formed from any nonmagnetic and nonconductivematerial such as plastic or the like.

Referring now to FIG. 7, in use, the primary coil 46 is positioned nearthe portion of the patient's 20 body wherein the orthopaedic device 14is implanted. The primary coil 46 is positioned such that the coil 46 issubstantially coplanar with the implanted orthopaedic device 14. Forexample, the primary coil 46 may be positioned such that the coil 46 andthe secondary coil 16 of the device 14 may be inductively coupled. To doso, a caregiver may grasp the sleeve 50 to move the primary coil 46 tothe desired location. In some embodiments, the primary coil 46 and thecore 48 are housed in a portable housing having a handle or the like tofacilitate the positioning of the primary coil 46. Once the primary coil26 is located in the desired position, an alternating current powersignal may be applied to the primary coil 46. In response to the powersignal, the primary coil 46 generates an alternating magnetic field. Thepower signal and primary coil 46 are configured such that thealternating magnetic field generated by the coil 26 extends into the leg18 or other portion of the patient 20. The magnetic field is received bythe secondary coil 16 of the implanted orthopaedic device 14. Asdiscussed above in regard to FIG. 1, the alternating magnetic fieldproduces a current in the secondary coil 26 which may be used to powerelectrical circuitry and/or devices coupled with the coil 26.

Referring now to FIG. 8, in one embodiment, the implantable orthopaedicdevice 14 includes a tibial tray 60. The tibial tray 60 is configured tobe coupled with a tibia of the patient 20 during a surgical proceduresuch as a total knee anthroplasty procedure. The tibial tray 60 includesa platform 62 for supporting a bearing insert 64. The insert 64 providesa bearing surface for a femur or femur implant to articulate. The tibialtray 60 also includes a stem portion 66 for securing the tray 60 to thetibia of the patient 60. The stem portion 66 is configured to beinserted into a resected end portion of the tibia and may be secured inplace by use of bone cement, although cementless configurations may alsobe used. The tibial tray 60 also includes a bobbin assembly 68 securedto a distal end of the stem portion 66. As illustrated in FIG. 9, thebobbin assembly 68 includes a screw head 70 having a hemispherical shapeand a bobbin 72 extending axially from the screw head 70 in thedirection of an axis 74. The bobbin assembly 68 also includes a threadportion 76 that extends axially from the bobbin 72 in the direction ofan axis 74. The bobbin assembly 68 may be formed from any nonmagneticmaterial such as a plastic material.

The secondary coil 16 is wound around the bobbin 72 of the bobbinassembly 68. Illustratively, solid wire is used to form the primary coil16, but in other embodiments, Litz wire may be used. Similar to theprimary coil 12, the secondary coil 16 is formed from a number ofindividual turns. The individual turns of the secondary coil 16 arewound around the bobbin 72 in a coil track 82. The dimensions of thebobbin 72 are based upon the particular application and implantableorthopaedic device 14 being used. For example, as illustrated in FIG.10, the bobbin 72 may have an outer diameter 80 and a coil track width84 sized based on the number of individual turns of the secondary coil16. That is, the outer diameter 80 and/or the coil track width 84 may beincreased to accommodate additional individual turns. To protect thesecondary coil 16, a sleeve 78 is configured to slide over the secondarycoil 16 when the bobbin assembly 68 is secured to the stem portion 66(via the thread portion 76). The sleeve 78 may also be formed from anytype of nonmagnetic material such as a plastic or rubber material.

As discussed in more detail below in regard to FIG. 11, the implantableorthopaedic device 14 may also include additional electronic circuitryand/or devices. The secondary coil 16 provides power to such electroniccircuitry and devices. In some embodiments, the additional electroniccircuitry is coupled with the insert 64 (e.g., embedded in the insert64). In other embodiments, the electronic circuitry may be coupled withthe tibial tray 60. Regardless, wires or other interconnects from thesecondary coil 16 may be routed up through the stem portion 66 of thetibial tray 60 and coupled with the electronic circuitry and/or devices.

Referring now to FIG. 11, in one embodiment, the power circuit 22 of thesystem 10 includes a waveform generator 90, an amplifier 92, and a meter94. The waveform generator 90 is coupled with the amplifier 92 via anumber of interconnects 96. The interconnects 96 may be embodied as anytype of interconnects capable of providing electrical connection betweenthe generator 90 and the amplifier 92 such as, for example, wires,cables, PCB traces, or the like. The waveform generator 90 may be anytype of waveform generator that is capable of producing an output signalhaving a frequency that matches the resonant frequency of the primarycoil 12, 26, 46. For example, the waveform generator 90 may be formedfrom discrete and/or integrated circuitry. Alternatively, the waveformgenerator 90 may be formed from a stand-alone waveform generationdevice. For example, in one embodiment, the waveform generator 90 isembodied as a PCI-5401 Single Channel Arbitrary Function Generator forPCI commercially available from National Instruments of Austin, Tex.

The amplifier 92 is configured to amplify the output signal receivedfrom the generator 90 and produce an amplified output signal having apredetermined amplitude. The predetermined amplitude of the amplifiedoutput signal may be determined based on the particular primary coil 12,26, 46 used and/or the application of the system 10. For example, inembodiments including primary coil 26, an amplified output signal havinga higher amplitude may be used due to the increased distance between thecoil 26 and the secondary coil 16. Comparatively, in embodimentsincluding primary coil 46, an amplified output signal having a loweramplitude may be used due to the increased inductive coupling efficiencyprovided by the core 48. The amplifier 92 may be any type of amplifiercapable of amplifying the output signal of the waveform generator to thepredetermined amplitude. For example, the amplifier 92 may be formedfrom discrete and/or integrated circuitry. Alternatively, the amplifier92 may be formed from a stand-alone amplification device. For example,in one embodiment, the amplifier 92 is embodied as a model AR-700A1Amplifier commercially available from Amplifier Research of Souderton,Pa.

The meter 94 is coupled with the amplifier 92 via a number ofinterconnects 98 and to the primary coil 12, 26, 46 via theinterconnects 24. The interconnects 98 may be embodied as any type ofinterconnects capable of providing electrical connection between themeter 94 and the amplifier 92 such as, for example, wires, cables, PCBtraces, or the like. The meter 94 is configured to measure the amount ofpower supplied to (i.e., used by) the primary coil 12, 26, 46. In someembodiments, the meter 94 is coupled in parallel with the outputs of theamplifier 94 (i.e., the amplifier 92 is coupled directly to the primarycoil 12, 26, 46 and to the meter 94). In other embodiments, the meter 94may have a pass-through input-output configuration. Regardless, themeter 94 has a large input impedance such that the effects of the meter94 on the amplified power signal are reduced. The meter 94 may be anytype of meter capable of measuring the power supplied to the primarycoil 12, 26, 46. For example, the amplifier 92 may be formed fromdiscrete and/or integrated circuitry. Alternatively, the amplifier 92may be formed from a stand-alone amplification device. For example, inone embodiment, the meter 94 is embodied as Model 2330 Sampling WattMeter commercially available from Clarke-Hess Communication ResearchCorporation of Long Island City, N.Y.

In some embodiments, the power circuit 22 may also include a controlcircuit 100, a display 102, and a receiver 104. The control circuit 100may be communicatively coupled with the meter 94 via a number ofinterconnects 106, with the display 102 via a number of interconnects108, and with the receiver 104 via a number of interconnects 110. Thecontrol circuit 100 may be embodied as any type of control circuitcapable of performing the functions described herein including, but notlimited to, discrete circuitry and/or integrated circuitry such as aprocessor, microcontroller, or an application specific integratedcircuit (ASIC). The receiver 104 is configured to wirelessly receivedata from the implantable orthopaedic device 14 and transmit the data tothe control circuit 100. The control circuit 100 may display the data,or computed data based thereon, on the display 102. Additionally, thecontrol circuit 100 may display power usage data received from the meter94 on the display 102. The display 102 may be embodied as any type ofdisplay capable displaying data to the caregiver including, for example,a segmented light emitting diode (LED) display, a liquid crystal display(LCD), or the like.

The power circuit 22 is coupled with the primary coil 12, 26, 46 via theinterconnects 24. In embodiments including the primary coil 46, theprimary coil 46 includes the substantially “C”-shaped core 48. A tuningcapacitor 112 is coupled in parallel with the primary coil 12, 26, 46(i.e., the capacitor 112 and the primary coil 12, 26, 46 form a parallelresonance circuit). The tuning capacitor 112 is used to configure theresonant frequency of the primary coil 12, 26, 46. That is, thecapacitance value of the tuning capacitor 112 is selected such that theresulting resonant frequency of the primary coil 12, 26, 46 matches theresonant frequency of the secondary coil 16. In addition, in someembodiments, the turning capacitor 112 is selected such that the qualityfactor (Q) of the resulting resonance curve is high. In suchembodiments, the resonant frequency of the primary coil 12, 26, 46matches a narrower bandwidth of frequencies.

In some embodiments, the tuning capacitor 112 is physically coupled to aportion (e.g., bobbin 32) of the primary coil 12, 26, 46 such that thetuning capacitor 112 moves with the primary coil 12, 26, 46. In otherembodiments, the tuning capacitor 112 may be included in the powercircuit 22. Alternatively, the tuning capacitor 112 may be separate fromboth the power circuit 22 and the primary coil 12, 26, 46. Additionally,in some embodiments, the tuning capacitor 112 is embodied as acapacitive device having a variable capacitance value. In suchembodiments, the resonant frequency of the primary coil 12, 26, 46 maybe adjusted to match the resonant frequency of other secondary coils byadjusting the capacitance value of the capacitor 112 and reconfiguringthe resonant frequency of the power signal. The degree to which theresonant frequency of the primary coil 12, 26, 46 can be tuned isdependant up the granularity of the capacitance values obtainable withthe variable capacitive device (i.e., the selection of availablecapacitance values). However, fine tuning of the resonant frequency maybe accomplished by configuring the frequency of the power signal via thewaveform generator 90. In one embodiment, the tuning capacitor 112 isembodied as a CS-301 Capacitance Substituter commercially available fromIET Labs, Incorporated of Westbury, N.Y.

The implantable orthopaedic device 14 includes the secondary coil 16, atuning capacitor 116 coupled in series with the secondary coil 16, andan implanted electrical device 118 coupled in parallel with thesecondary coil 16 and the tuning capacitor 116. The capacitor 116 andthe secondary coil 16 form a series resonance circuit. The tuningcapacitor 116 is used to configure the resonant frequency of thesecondary coil 116. That is, the capacitance value of the tuningcapacitor 116 is selected such that the resulting resonant frequency ofthe secondary coil 16 is equal to a predetermined frequency. Inaddition, in some embodiments, the turning capacitor 116 is selectedsuch that the quality factor (Q) of the resulting resonance curve islow. In such embodiments, the resonant frequency of the secondary coil16 matches a broader bandwidth of frequencies.

The implanted electrical device 118 may be embodied as any electricalcircuit(s), electrical device(s), or combination thereof, capable ofbeing housed in or on the implantable orthopaedic device 14 and poweredby the current produced by the secondary coil 16. For example, theimplanted electrical device 118 may include, but is not limited to,sensors such as magnetic sensors, load sensors, chemical sensors,biological sensors, and/or temperature sensors; processors or othercircuits; electrical motors; actuators; and the like. In one embodiment,the implanted electrical device 118 is embodied as an anisotropicmagneto resistive sensor (AMR sensor). In one particular embodiment, theimplanted electrical device 118 is embodied as an HMC1023 3-axisMagnetic Sensor commercially available from Honeywell International,Incorporated of Morristown, N.J. It should be appreciated that theimplanted electrical device 118 receives power only while the primarycoil 12, 26, 48 is energized via the power signal to produce thealternating magnetic field and the secondary coil 16 is exposed to thealternating magnetic field such that a current is induced in thesecondary coil 16.

In some embodiments, the implantable orthopaedic device 14 may alsoinclude a transmitter 120. The transmitter 120 is coupled incommunication with the implanted electrical device 118 via a number ofinterconnects 122 and receives power from the secondary coil 16 in amanner similar to the device 118. The transmitter 120 is configured totransmit data received from the implanted electrical device 118 to thereceiver 104 of the power circuit 22 via a wireless communication link124. For example, in embodiments wherein the implanted electrical device118 is a pressure sensor, the transmitter 120 is configured to transmitpressure data received from the device 118 to the receiver 104. Inresponse, the control circuit may be configured to display the pressuredata to the caregiver on the display 102. The transmitter 120 maytransmit the data to the receiver 104 using any suitable wirelesscommunication protocol such as, for example, Bluetooth, wireless USB,Wi-Fi, WiMax, Zigbee, or the like.

The implantable orthopaedic device 14 may also include an energy storagedevice 126. The energy storage device 126 may be embodied as any devicecapable of storing an amount of energy for later use by the implantedelectrical device 118. For example, the energy storage device 126 may beembodied as a rechargeable battery such as a nickel cadmium battery or astorage capacitor and associated circuitry. Regardless, the energystorage device 126 is configured to be charged (i.e., energy is storedin the device 126) while the orthopaedic device 14 is being powered bythe cooperation of the power circuit 22, the primary 12, 26, 46, and thesecondary coil 16. Once the device 14 is no longer receiving power fromthe secondary coil 16, the energy storage device 126 begins providingpower to the implanted electrical device 118. Once the energy storagedevice 126 becomes drained of energy, the device 126 may be rechargedvia the power circuit 22 and the primary coil 12, 26, 46. In this way,the device 118 may be powered over long periods of time.

Referring now to FIG. 12, in one embodiment, the power circuit 22 andprimary coil 12, 26, 46 are positioned in a portable housing 130. Insome embodiments, the portable housing 130 is embodied as a hand-heldhousing, which facilitates the positioning of the power circuit 22 andprimary coil 12, 26, 46 by the caregiver. In such embodiments thecaregiver may quickly reposition the primary coil 12, 26, 46, move orsweep the primary coil 12, 26, 46 over a portion of the patient 20 andtransport the power circuit 22 and the primary coil 12, 26, 46 to a newlocation. To further facilitate portability, in such embodiments, thepower circuit 22 includes a direct current (DC) power source 132, suchas rechargeable or replaceable batteries. Accordingly, the housing 130may be moved about the patient 20 without the need of an AC cord or ACpower outlet.

The power circuit 22 also includes a converter 134 coupled with thepower source 132 via a number of interconnects 136. The converter 134 isconfigured to convert the DC power signal received from the DC powersource 132 to an AC power signal. The converter 134 may be embodied asany circuit or device capable of converting the DC power signal to a ACpower signal including, for example, discrete circuitry, integratedcircuitry, or a combination thereof. A frequency multiplier 138 iscoupled with the converter 134 via a number of interconnects 140. Thefrequency multiplier 138 is configured to convert the AC power signalreceived from the converter 134 to an AC power signal having apredetermined frequency. That is, the frequency multiplier 138 producesan AC power signal having a frequency that matches the resonantfrequency of the primary coil 12, 26, 46. The frequency multiplier 138may be embodied as any circuit or device capable of multiplying thefrequency of the AC power signal by a predetermined amount.

The power circuit 22 also includes an amplifier 142 coupled with thefrequency multiplier 138 via a number of interconnects 144. Theamplifier 142 is configured to amplify the output signal received fromthe frequency multiplier 138 and produce an amplified output signalhaving a predetermined amplitude. The predetermined amplitude of theamplified output signal may be determined based on the particularprimary coil 12, 26, 46 used and the application of the system 10. Theamplifier 142 may be embodied as any type of amplifier capable ofamplifying the output signal of the frequency multiplier 138 to thepredetermined amplitude. For example, the amplifier 142 may be formedfrom discrete and/or integrated circuitry.

A measuring circuit 146 is coupled with the amplifier 142 via a numberof interconnects 148 and to the primary coil 12, 26, 46 via theinterconnects 24. The measuring circuit 146 is configured to measure theamount of power supplied to the primary coil 12, 26, 46. In someembodiments, the meter 94 is coupled in parallel with the outputs of theamplifier 144 (i.e., the amplifier 142 is coupled directly to theprimary coil 12, 26, 46 and to the measuring circuit 146). In otherembodiments, the measuring circuit 146 may have a pass-throughinput-output configuration. Regardless, the measuring circuit 146 has alarge input impedance such that the effects of the measuring circuit 146on the amplified power signal are reduced. The measuring circuit 146 maybe any type of measuring circuit capable of measuring the power suppliedto the primary coil 12, 26, 46. For example, the measuring circuit 146may be formed from discrete and/or integrated circuitry.

A control circuit 150 is communicatively coupled with the measuringcircuit 146 via a number of interconnects 152, with a display 154 via anumber of interconnects 156, and with a receiver 158 via a number ofinterconnects 160. The control circuit 150 may be similar to the controlcircuit 100 described above in regard to FIG. 11. The control circuit150 may be embodied as any type of control circuit capable of performingthe functions described herein including, but not limited to, discretecircuitry and/or integrated circuitry such as a processor,microcontroller, or an application specific integrated circuit (ASIC).The receiver 158 is configured to wirelessly receive data from theimplantable orthopaedic device 14 and transmit the data to the controlcircuit 150. The control circuit 150 may display the data, or computeddata based thereon, on the display 154. Additionally, the controlcircuit 150 may display power usage data received from the measuringcircuit 146 on the display 154. The display 154 may be embodied as anytype of display capable displaying data to the caregiver including, forexample, a segmented light emitting diode (LED) display, a liquidcrystal display (LCD), or the like.

In addition to the power circuit 22, the primary coil 12, 26, 46 (andthe core 48 in some embodiments) and the tuning capacitor 112 arepositioned in the portable housing 130. As discussed above in regard toFIG. 11, the tuning capacitor 112 is used to configure the resonantfrequency of the primary coil 12, 26, 46 and, in some embodiments, isselected such that the quality factor (Q) of the resulting resonancecurve is high. The tuning capacitor 112 may be physically coupled to aportion (e.g., bobbin 32) of the primary coil 12, 26, 46 or may beseparate from the primary coil 12, 26, 46. Regardless, the tuningcapacitor 112 is coupled in parallel with the primary coil 12, 26, 46 toform a parallel resonance circuit.

Although illustrated and described above as separate components, itshould be appreciated that any two or more of the power source 132, theconverter 134, the frequency multiplier 138, the amplifier 142, themeasuring circuit 146, the control circuit 150, the display 154, and thereceiver 158 may be included as a single component capable of performingthe functions of the individual components. For example, in someembodiments, the converter 134 and the frequency multiplier 138 may beembodied as a single circuit, integrated or discrete, that is capable ofconverting the DC power signal from the power source 132 to an AC powersignal having a frequency that matches the resonant frequency of theassociated primary coil 12, 26, 46. As such, the interconnects 136, 140,144, 148, 152, 156, 160 may be embodied as any type of interconnectscapable of providing electrical connection between the variouscomponents of the power circuit 22 such as, for example, wires, cables,PCB traces, internal integrated circuit connections, or the like.

Referring now to FIG. 13, an algorithm 200 for transcutaneouslytransferring an amount of energy to the implantable orthopaedic device14 begins with a process step 202. In step 202, the resonant frequencyof the primary coil 12, 26, 46 is configured to match the resonantfrequency of the secondary coil 16 in the implantable device 14. Forexample, the tuning capacitor 112 may be selected or replaced such thatthe resulting resonant frequency of the primary coil 12, 26, 46 matchesthe resonant frequency of the secondary coil 16. In embodiments, whereinthe tuning capacitor 112 is embodied as a variable capacitor, thecapacitance of the tuning capacitor 112 may be adjusted to match thefrequencies of the primary coil 12, 26, 46 and the secondary coil 16. Asdiscussed above in regard to FIGS. 11 and 12, the turning capacitor 112may be selected such that the quality factor (Q) of the resultingresonance curve is high. That is, the resonant frequency of the primarycoil 12, 26, 46 matches a narrower bandwidth of frequencies.

In some embodiments, the resonant frequency of the secondary coil 16 ofthe implantable orthopaedic device 14 is predetermined based on the typeof orthopaedic device 14. For example, all knee implants may beconfigured to a resonant frequency of about 5 kilohertz while all hipimplants may be configured to a resonant frequency of about 4 kilohertz.In such embodiments, the resonant frequency of the secondary coil 16 mayalready be configured to the predetermined frequency. In addition, inembodiments wherein the orthopaedic device 14 has been previouslyimplanted in the patient 20, the resonant frequency of the secondarycoil is also predetermined (i.e., pre-configured prior to the surgicalprocedure). However, in other embodiments or applications, such as whenthe orthopaedic device 14 has not yet been implanted into the patient20, the resonant frequency of the secondary coil 16 may be configured.To do so, as discussed above in regard to FIG. 11, the capacitance valueof the tuning capacitor 116 is selected such that the resulting resonantfrequency of the secondary coil 16 matches a predetermined frequency(e.g., 5 kilohertz). Additionally, the turning capacitor 116 may beselected such that the quality factor (Q) of the resulting resonancecurve is low. That is, the resonant frequency of the secondary coil 16matches a broad bandwidth of frequencies.

Once the resonant frequency of the primary coil 12, 26, 46 (and, in someembodiments, the secondary coil 16) has been configured, the algorithm200 advances to process step 204. In process step 204, the power signalis configured. That is, the frequency of the power signal is configuredto match the resonant frequency of the primary coil 12, 26, 46. To doso, the waveform generator 90 or the frequency multiplier 138 may beconfigured to produce an output signal having a frequency that matchesthe resonant frequency of the primary coil 12, 26, 46. For example, ifthe resonant frequency of the primary coil 12, 26, 46 is configured to 6kilohertz, the waveform generator or the frequency multiplier 138 isconfigured to produce an output signal having a frequency of about 6kilohertz.

Once the resonant frequency of the power signal has been matched to theresonant frequency of the primary coil 12, 26, 46, the primary coil 12,26, 46 is positioned in process step 206. To do so, in embodimentsincluding the primary coil 26, the portion of the patient 20 (e.g., leg18) wherein the implantable orthopaedic device 14 is located ispositioned in the aperture 28 such that the primary coil 26circumferentially surrounds the portion of the patient 20. The primarycoil 26 is then positioned such that the primary coil 26 issubstantially coplanar with the implanted orthopaedic device 14. Becausethe aperture 28 has a diameter 30 greater than the width of the portionof the patient 20, the primary coil 26 may be positioned such that coil26 is spaced away from the skin of the patient 20 to reduce thelikelihood of damaging the skin of the patient 20. To position theprimary coil 26 in the desired location, the caregiver may grasp thebobbin 32 or handle 38 to move the coil 26.

Alternatively, in embodiments including the primary coil 46, the primarycoil 46 may be positioned near the portion of the patient 20 (e.g., leg18) wherein the implantable orthopaedic device 14 is located. Theprimary coil 46 is positioned such that the primary coil 46 issubstantially coplanar with the orthopaedic device 14. The primary coil46 may also be spaced away from the skin of the patient 20 to reduce thelikelihood of damaging the skin of the patient 20. To position theprimary coil 46 in the desired location, the caregiver may grasp thesleeve 56 or a portion of the core 48 to move the coil 46.

In embodiments wherein the power circuit 22 and the primary coil 12, 26,46 are positioned in a portable housing 130, the caregiver may positionthe primary coil 12, 26, 46 may positioning the portable housing 130such that the housing 130 (i.e., the primary coil 12, 26, 46 locatedwithin the housing 130) is near and substantially coplanar with theimplantable orthopaedic device 14. To do so, the caregiver may grasp thehousing 130, or a handle coupled therewith, to move the housing 130 andthe primary coil 12, 26, 46 to the desired location.

Once the primary coil 12, 26, 46 has been positioned at the desiredlocation, the primary coil 12, 26, 46 is energized via a power signalfrom the power circuit 22 in process step 208. In response, the primarycoil 12, 26, 46 generates an alternating magnetic field. The alternatingmagnetic field is received by the secondary coil 16 (i.e., the secondarycoil 16 is exposed to the magnetic field) and the primary coil 12, 26,46 and the secondary coil 16 become inductively coupled. Because thesecondary coil 16 is exposed to an alternating magnetic field, a currentis induced in the secondary coil 16. In this way, the secondary coil 16provides power to the implanted electrical device(s) and other circuitryof the implantable orthopaedic device 14. Because the resonantfrequencies of the power signal, the primary coil 12, 26, 46, and thesecondary coil 16 are matched; the transfer efficiency of energy fromthe primary coil 12, 26, 46 to the secondary coil 16 is increased. Inembodiments including the display 102 or display 154, the power suppliedto the primary coil 12, 26, 46 may be displayed to the caregiver.

Additionally, in some embodiments, the algorithm 200 may include aprocess step 210 in which data is received from the implantableorthopaedic device 14. The received data may be any type of dataobtained by or produced by the implanted electrical device 118. Forexample, in embodiments wherein the implanted electrical device 118 isembodied as a sensor, sensory data may be received by the receiver 104from the transmitter 120 of the orthopaedic device 14. In someembodiments, the implanted electrical device 118 is configured tomeasure or determine the data while receiving power from the secondarycoil 16. In other embodiments, such as in embodiments including theenergy storage device 126, the implanted electrical device 118 may beconfigured to continually or periodically measure or determine the data.Regardless, the data so determined is transmitted to the power circuit22 via the wireless link 124.

Once the data is received by the power circuit 22 (via the receiver 104,158), the data may be displayed to the caregiver via the associateddisplay 102, 154 in process step 212. To do so, the control circuit 100,150 may control the display 102, 154 to display the data. In addition,the control circuit 100, 150 may be configured to process the data todetermine additional data based on the data received from theorthopaedic device 14.

Referring now to FIG. 14, an algorithm 220 for determining a location ofan orthopaedic device implanted in a patient's body begins with aprocess step 222. In the process step 222, the primary coil 12, 26, 46is positioned in a new location. That is, in the first iteration of thealgorithm 220, the primary coil 12, 26, 46 is positioned in an initiallocation near the portion of the patient 20 wherein the orthopaedicdevice 14 is implanted. To do so, in embodiments including the primarycoil 26, the portion of the patient 20 (e.g., leg 18) wherein theimplanted orthopaedic device 14 is located is positioned in the aperture28 such that the primary coil 26 circumferentially surrounds the portionof the patient 20. Alternatively, in embodiments including the primarycoil 46, the primary coil 46 is positioned near the portion of thepatient 20 (e.g., leg 18) wherein the orthopaedic device 14 isimplanted. Because the exact location of the orthopaedic device 14 maynot be known, the primary coil 12, 26, 46 may not be substantiallycoplanar with the orthopaedic device 14 during the first iteration ofthe algorithm 220 (i.e., while the primary coil 12, 26, 46 is at theinitial location).

Once the primary coil 12, 26, 46 is positioned in the initial locationin step 222, the power usage of the primary coil 12, 26, 46 isdetermined in process step 224. To do so, the meter 94 or measuringcircuit 146 determines the power supplied to the primary coil 12, 26,46. In some embodiments, the power supplied to the primary coil 12, 26,46 may also be displayed to the caregiver via the display 102, 154. Thepower usage of the primary coil 12, 26, 46 varies according to theinductive coupling of the primary coil 12, 26, 46 and the secondary coil16. That is, as the secondary coil 16 draws power from the alternatingmagnetic field, the primary coil 12, 26, 46 uses an increased amount ofpower to maintain the alternating magnetic field. Accordingly, the powerusage of the primary coil 12, 26, 46 increases as the primary coil 12,26, 46 becomes more coplanar, and more inductively coupled, with thesecondary coil 16.

In process step 226, the algorithm 220 determines if the power usage atthe present location of the primary coil 12, 26, 46 is at or above apredetermined threshold value (e.g., a user defined maximum value). Todo so, the control circuit 100, 150 may be configured to storepreviously measured power usage amounts in a memory device. The powerusage of the primary coil 12, 26, 46 at the present location may then becompared to the stored power usage amounts. If the power usage of theprimary coil 12, 26, 46 at the present location is not at or above thepredetermined threshold value, the algorithm 220 loops back to theprocess step 222 in which the primary coil 12, 26, 46 is positioned in anew location. It should be appreciated that the process steps 222, 224,226 may be repeated until a location is found at which the powersupplied to the primary coil 12, 26, 46 is at or above the predeterminedthreshold. For example, a caregiver may move or sweep the primary coil12, 26, 46 over the location of the patient 20 wherein the orthopaedicdevice 14 is implanted. As the caregiver sweeps the primary coil 12, 26,46 over the patient 20, the power usage of the primary coil 12, 26, 46varies. A location at which the power supplied to the primary coil 12,26, 46 is at or above the predetermined threshold value may bedetermined by monitoring the display 102, 104. Alternatively, in someembodiments, the power circuit 22 may include an audible or visualindicator that is activated when the primary coil 12, 26, 46 sweeps overa location at which the power supplied to the primary coil 12, 26, 46 isat or above a predetermined threshold value.

The location(s) at which the power usage of primary coil 12, 26, 46 isat or above the predetermined threshold value correlates to a locationat which the primary coil 12, 26, 46 is substantially coplanar with thesecondary coil 16 of the implanted orthopaedic device 14. Accordingly,once such a location is found, the location of the implanted orthopaedicdevice 14 is recorded in process step 228. The location of the device 14may be recorded by, for example, establishing a mark on the skin of thepatient 20, recording coordinate data identifying the location of thedevice 14, or the like.

While the disclosure has been illustrated and described in detail in thedrawings and foregoing description, such an illustration and descriptionis to be considered as exemplary and not restrictive in character, itbeing understood that only illustrative embodiments have been shown anddescribed and that all changes and modifications that come within thespirit of the disclosure are desired to be protected.

There are a plurality of advantages of the present disclosure arisingfrom the various features of the systems and methods described herein.It will be noted that alternative embodiments of the systems and methodsof the present disclosure may not include all of the features describedyet still benefit from at least some of the advantages of such features.Those of ordinary skill in the art may readily devise their ownimplementations of the systems and methods that incorporate one or moreof the features of the present invention and fall within the spirit andscope of the present disclosure as defined by the appended claims.

1. A limb brace comprising: a brace structure configured to be coupledto a limb of a patient; a primary coil coupled to the brace structureand having a resonant frequency; and means for matching the resonantfrequency of the primary coil to a resonant frequency of a secondarycoil spaced apart from the brace structure and coupled to an implantableorthopaedic device.
 2. The limb brace of claim 1, wherein the primarycoil is configured to circumferentially surround a portion of the limbof the patient while the brace structure is coupled to the limb.
 3. Thelimb brace of claim 1, wherein the primary coil is a toroidal primarycoil.
 4. The limb brace of claim 1, wherein the primary coil is woundaround a portion of a “C”-shaped ferrite core.
 5. The limb brace ofclaim 1, wherein the primary coil is configured to be inductivelycouplable with the secondary coil while the brace structure is coupledto the limb of the patient.
 6. The limb brace of claim 1, wherein theprimary coil is configured to be spaced away from a skin surface of thelimb while the brace structure is coupled to the limb of the patient. 7.The limb brace of claim 1, wherein the resonant frequency of the primarycoil is adjustable to match the resonant frequency of a differentsecondary coil of an implantable orthopaedic device.
 8. The limb braceof claim 1, wherein the resonant frequency of the primary coil is lessthan about 9 kilohertz.
 9. The limb brace of claim 8, wherein theresonant frequency of the primary coil is about 5 kilohertz.
 10. Thelimb brace of claim 1, wherein the brace structure is configured tocouple to a leg of the patient.
 11. An apparatus, comprising: a bracestructure configured to be coupled to a limb of a patient; a primarycoil coupled to the brace structure; an implantable orthopaedic device;a secondary coil coupled to the implantable orthopaedic device; andwherein the primary coil has a resonant frequency matched to a resonantfrequency of the secondary coil.
 12. The apparatus of claim 11, whereinthe primary coil is configured to circumferentially surround a portionof the limb of the patient while the brace structure is coupled to thelimb.
 13. The apparatus of claim 11, wherein the primary coil is atoroidal primary coil.
 14. The apparatus of claim 11, wherein theprimary coil is wound around a portion of a “C”-shaped ferrite core. 15.The apparatus of claim 11, wherein the primary coil is configured to beinductively couplable with the secondary coil while the brace structureis coupled to the limb of the patient.
 16. The apparatus of claim 11,wherein the primary coil is configured to be spaced away from a skinsurface of the limb while the brace structure is coupled to the limb ofthe patient.
 17. The apparatus of claim 11, wherein the resonantfrequency of the primary coil is adjustable to match the resonantfrequency of a different secondary coil coupled to the implantableorthopaedic device.
 18. The apparatus of claim 11, wherein the resonantfrequency of the primary coil is less than about 9 kilohertz.
 19. Theapparatus of claim 18, wherein the resonant frequency of the primarycoil is about 5 kilohertz.
 20. The apparatus claim 11, wherein the bracestructure is configured to couple to a leg of the patient.